The present invention relates generally to X-ray imaging machines, and particularly to a stationary tomographic mammography system.
A traditional X-ray imaging system includes an X-ray source and a detector array for generating an internal image of an object. As is well known, the X-ray source generates X-rays, which are attenuated by the object (i.e. they either pass through the object or are absorbed therein). As a result, the transmitted X-rays vary in intensity. The detector array receives and measures the resultant X-ray flux so as to generate electrical signals necessary for constructing an internal image of the object.
In at least one known mammography imaging system, an X-ray source projects a fan-shaped beam, which is collimated to lie within an X-Y plane of a Cartesian coordinate system and is generally referred to as the “imaging plane.” The X-ray beam passes through the object being imaged, such as a patient's breast. The beam, after being attenuated by the object, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is dependent upon the attenuation of the X-ray beam by the object. Each detector element of the array generates a separate electrical signal that is a measurement of the beam attenuation at the detector location. The attenuation measurements from all the detectors are acquired separately to generate a transmission profile or detector signals.
Conventional film and digital detector mammography systems traditionally utilize mount mechanisms, which allow the user to manually or robotically pivot an X-ray source. This pivoting allows generation of different projection views during imaging of an individual patient breast. During this operation, the patient breasts are held by a breast compression system, which remains stationary during X-ray source movements.
In certain digital mammographic applications, such as tomography, a series of images is rapidly acquired through a sweep of projection angles, which may include 60° or more. The images are taken quickly to minimize anatomical movement and patient compression time.
However, the mechanical motion required to move the X-ray source may induce image motion artifacts and may also require sub-optimal trade-offs between X-ray source arm acceleration mechanics and overall system ergonomics.
Special considerations are currently implemented to avoid patient and operator collisions when an X-ray source, mounted on a robotic arm, is operated. In contrast, if the X-ray source is manually moved to each projection angle, the patient may sustain extended compression times, which may be undesireable. In addition, certain rapid multi-view applications may require that the X-ray source be completely stationary during the actual exposure thereby necessitating acceleration and deceleration of the angular movement.
Because very sensitive flat panel X-detectors are often utilized in such systems, it is also known that even moderate levels of shock and vibration applied to their panel read-out interconnection systems may cause image artifacts to be generated. In addition, the servo motor used to move the X-ray source to the required angles must not cause any appreciable magnetic fields to be induced into the sensitive X-ray detector or additional artifacts may be generated.
The disadvantages associated with current imaging systems have made it apparent that a new technique for mammographic imaging is needed. The new technique should minimize vibration and scan time. The present invention is directed to these ends.